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Lubricant Contribution to Energy Efficiency
Published in Don M. Pirro, Martin Webster, Ekkehard Daschner, Lubrication Fundamentals, 2017
Don M. Pirro, Martin Webster, Ekkehard Daschner
The second class of friction modifier additives is typically based on a metal that chemically reacts with the surface creating a new layer or surface. Molybdenum (Mo) is the most widely used metal although others such as tungsten can also be used. The metal is often combined with other elements such as sulfur and oxygen, which, when coupled with alkyl chains, makes the molecule soluble in lubricant base stocks. In order for this class of additive to perform its function, it is often necessary for a direct reaction with the surface to occur. For oil-soluble molybdenum-containing additives, the friction-reducing effect is associated with the formation of molybdenum disulfide (MoS2) on the surface. The layered structure of MoS2 resembles graphite and provides a plane along which it is easy for one layer to slide over its neighbors. These easily sheared layers that form in the junctions between asperity contacts reduce the shear stress required for asperities to slide past on another, resulting in lower friction. It has been observed that the formation of MoS2 occurs only within the rubbing track of the surface. The precise nature of the chemical and physical processes leading to the formation of reacted films remains an area of study, but the use of such additives provides an effective means of reducing friction.
2, a Lubricant Additive for Environmentally Friendly Lubricants
Published in Brajendra K. Sharma, Girma Biresaw, Environmentally Friendly and Biobased Lubricants, 2016
Sudeep Ingole, Archana Charanpahari, Suresh Umare
A typical lubricant consists of additives such as antiwear, friction modifier, and EP for its effective functioning. Antiwear and EP additives are certain types of chemical compounds which provide good boundary lubrication and have the ability to build strong boundary lubricant layers during extreme events (i.e., severe loading conditions). They protect sliding surfaces from indenting by the asperities of opposite surface. From the mechanical properties point of view, antiwear and EP additives are semiplastic deposits with high shear strength and show moderate to high COF [1]. ZDDPs are antiwear/EP additives. Friction modifiers, on the other hand, are composed of orderly and closely packed layered structure of multimolecules. They will have the polar head attached to the metallic surface and intermolecular layers are loosely adhered to each other. This structure of friction modifier produces lower COF [1]. Molybdenum disulfide (MoS2) is a friction modifier. Other additives include VI improvers, rust and oxidation inhibitors, anticorrosion agents, and antifoaming agents.
Tribology of Automotive Components
Published in Ahmed Abdelbary, Extreme Tribology, 2020
In general, ATF are formulated using a synthetic or mineral oil base stock plus a variety of additives. Such additives include friction modifiers to produce the desired clutch operation, corrosion inhibitors, viscosity index improvers, dispersants, seal swell agents, antioxidants and anti-wear agents, with a total additive treatment level typically in the range of 10 to 20% (Kemp and Linden, 1990; Lann et al., 2000). It is important to mention that friction modifiers have particular importance for proper transmission performance. Long-chain hydrocarbon molecules with a polar group on one end are usually employed to produce good clutch friction characteristics. Dilauryl phosphate and oleic acid are typical examples of friction-modifier additives.
Moving towards green lubrication: tribological behavior and chemical characterization of spent coffee grounds oil
Published in Green Chemistry Letters and Reviews, 2023
Jessica Pichler, Rosa Maria Eder, Lukas Widder, Markus Varga, Martina Marchetti-Deschmann, Marcella Frauscher
Nanotribometer and rheometer experiments on S-CRUP. For the nanotribometer measurements, the lowest COF can be observed for the tribo-experiments on unpolished 100Cr6 discs S-CRUP (Figure 10). Superior to the other materials tested, S-CRUP samples display excellent repeatability with a very low margin of deviation between data points for all three applied lubricants. For this reason, the S-CRUP surface was chosen for further tribological testing on the rheometer. The SCGO exhibits lower COF deriving from long and polar fatty acid chains (µmean = 0.092 100% SCGO; µmean = 0.095 5% SCGO; µmean = 0.129 PAO 8), which are strongly attracted to metallic surfaces. These components are lacking in PAO, a pure hydrocarbon base oil. The ability of SCGO to reduce friction also in the 5% dilution makes it attractive for use as friction modifying boundary lubrication additive. A common friction modifier usually consists of a polar head group and a non-polar tail, creating a cushion between the metal surfaces.
Friction and normal forces of model friction modifier additives in simulations of boundary lubrication
Published in Molecular Physics, 2019
Michael L. Greenfield, Hiroko Ohtani
Boundary lubrication also arises in automotive applications. Automatic transmission fluids and other driveline fluids rely on surface-active additives in order to achieve their boundary lubrication properties [25]. A friction modifier (FM) is a key additive in automatic transmission fluids, where it controls the frictional profiles of wet clutch systems. It reduces the static coefficient of friction, and it changes the dependence of friction on velocity such that sliding friction is higher at higher speeds, rather than lower [26–29]. This is advantageous for stable operation of advanced automatic transmission designs without stick–slip or shudder, which tends to result in noise and additional stress on other parts of the transmission [30].
Effect of additives on a surface textured piston ring–cylinder liner system
Published in Tribology - Materials, Surfaces & Interfaces, 2019
Zinc diethyl dithiophosphate (ZDDP), a commonly used organometallic antiwear lubricant additive forms around 18 mg/l of sulphur oxides and 9 mg/l of phosphorus oxides [2]. Molybdenum dithiocarbamate (MoDTC) a friction modifier additive also contains sulphur. The mandate for the next generation engines is to achieve Tier 5 compliance, which can be attained by finding a key solution to reduce the amount of additives containing sulphur and phosphorus without compromising with efficiency.